According the specs I've seen, late 2005 should be the 1.5 ghz model. Either of the G4 models of the mini can be equipped with 1 meg so that's not conclusive. Seriously, the difference in speed between 1.5 and the earlier 1.42 ghz model would be difficult to notice....
The 1.5 model should have 64 meg graphics ram, double that of the 1.42 model.
